Patterns of brain morphology in mid-European Cyprinidae (Pisces, Teleostei): a quantitative histological study.

The present study considers patterns of brain morphology in 14 common species of mid-European Cyprinidae. Sixteen areas per brain were measured on serial cryostat sections by computer-aided planimetry. The volumes of these areas were expressed as % of the total brain volume. These brain centres (ranked according to falling values of the coefficient of variation VR, of the interspecific mean) are: Lobus facialis, L. vagus, central acustic area, Crista cerebellaris, Bulbus olfactorius, Eminentia granularis, Stratum opticum (of the optic tectum), Torus longitudinalis, Nucleus habenularis, Valvula cerebelli, Corpus cerebelli, Telencephalon, Tectum opticum, Diencephalon, Torus semicircularis, mesencephalic tegmentum. Seven primary sensory areas are leading in VR; highest in interspecific variability were the two special viscerosensory brainstem lobes for external (L. facialis) and internal (L. vagus) taste. Low in interspecific variability were integration centres (see above). By plotting the relative volumina of those brain centres which represent three major sensory modalities: brain stem chemosense, acoustico-lateralis and sense of vision, species are separated into three groups: 1) Most species scatter along an axis from moderately (Aspius aspius, Rutilus rutilus, Leuciscus cephalus, Scardinius erythrophthalmus, Alburnus alburnus, Chondrostoma nasus) to highly developed chemo- and acustico-lateralis centres (Vimba vimba, Abramis brama, Abramis ballerus). Blicca bjoercna is situated in the middle of this axis. Within the latter group the optic centres are evenly well developed. 2) Carassius carassius, Gobio gobio and Tinca tinca are characterized by relatively small acoustico-lateralis and optic areas, but highly developed chemocentres. 3) Pelecus cultratus is monotypic among the species investigated by having large acoustico-lateralis and optic, but modestly developed chemocentres. The brain patterns relative to life style are discussed.